Funds are requested for the purchase of an analytical electron microscope for use on three major research projects by five NIH supported investigators. The three project areas involve the determination of subcellular elemental distributions in studies of: 1) Basic mechanisms of contraction in cardiac muscle. 2) Salivary gland physiology particularly as related to Cystic Fibrosis. 3) The role of intracellular calcium stores in the control of ciliary activity. In these studies the common techniques employed are: 1) Specimen preparation via cryofixation, thin cryosectioning (100-200nm) and freeze drying. 2) High resolution imaging via conventional transmission and scanning transmission electron microscopy. 3) Quantitative elemental microanalysis via energy dispersive x-ray analysis. All three major projects are already underway on an existing JEOL 100C (purchased in 1976). Although this instrument is capable of generating excellent data, it is limited by its nature (oil diffusion pumped). More importantly, however, is the basic limitation of instrument time. The three major projects must share this instrument with several others including, for example, the engineering development of energy loss spectrometry instrumentation (particularly a prototype parallel detection system). Thus, productivity for all is severely limited. If this funding request is approved, a modern, ion pumped, analytical electron microscope will be utilized entirely by the three main projects listed. The existing instrument will then be devoted to: i) developmental projects including instrumental, technique, and new applications, ii) continuing smaller projects, and iii) training and support activities for the major projects. The overall effect of the increased access to this important technology will be to more than double the rate at which progress is made on the major projects while still allowing new instrumentation and new applications to be developed and smaller projects to continue.